short white screen after kernel boots

Andy Green andy at
Sat Nov 1 01:12:08 CET 2008

Hash: SHA1

Somebody in the thread at some point said:
| Michael 'Mickey' Lauer wrote:
|> Am Friday 31 October 2008 15:28:41 schrieb Andy Green:
|>> But the problems with white screen on boot are going to be solved a
|>> better way: Qi does not turn on the backlight and when the
|>> balaji-tracking stuff is used the backlight device is a child of the
|>> framebuffer, meaning the backlight will not be initialized until the
|>> framebuffer has been initialized.
|> Can we find out whether we have been jumpstarted by Qi or U-Boot? We
|> want to "polish" the turn-on-experience for the users still using U-Boot.
| Nothing specifically identifying the bootloader or its config is passed
| into the kernel.  However, something like this could be done in the
| command line passed to the kernel.  Qi might add "bootloader=Qi",
| signaling it's presence to user-space (and kernel).  Another possibility
| is to attempt to divine this information by checking the entire ATAG
| list passed in to the kernel; something as simple as the ordering of the
| tags might be sufficient to use as a "signature" to differentiate one
| from the other.
| (But I would prefer the command-line parameter, I think.)

If we want to do this then the commandline way is the way for sure, but
it makes me a bit worried that we start to make dependency in userspace
on something so esoteric as name of bootloader.

What I had in mind is not that userspace should bring up the backlight
(it will look like a brick then if you booted into a rootfs that didn't
know it was expected) but that the framebuffer driver will blank the
video memory and then bring up the backlight just after Glamo driver inits.

What we could do is chvt to 4 say and put a small logo in there during
glamo framebuffer init, just before backlight comes up?

- -Andy
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